MILK FROM DISEASED COWS. 35 



of the bacteria which were the original cause of the inflam- 

 mation in the mammary gland. The simple presence of 

 streptococci, however, does not necessarily indicate any dis- 

 eased condition of the udder, for streptococci are very com- 

 monly found in milk drawn from perfectly healthy udders. 



MILK FROM DISEASED COWS. 



The question has frequently been raised whether a cow 

 suffering from a bacterial disease that is not located in the 

 udder may transmit the bacteria through the milk glands 

 into her milk. Probably no definite answer can be given to 

 this question which would be true for all conditions. Cer- 

 tain forms of bacterial disease are located in somewhat 

 narrow centers ; for example, in the case of tubercular glands 

 in the neck. In these circumstances, provided there are no 

 tubercles in the udder, it is quite certain that the milk will 

 not contain tuberculosis bacilli. In the case of other infec- 

 tious diseases, like anthrax, the microorganisms enter the 

 circulatory system and pass all over the body in the blood, 

 and may be found even in the lymph. Under these condi- 

 tions the probability of the bacteria being secreted by the 

 milk is greater. The experiment has been occasionally 

 tried of injecting certain bacteria into the blood of animals 

 to determine whether they would be secreted through the 

 mammary glands (18). Although no universal answer can 

 yet be given to the question, the results appear to indicate 

 that the secretion of bacteria into the milk under these cir- 

 cumstances is extremely unusual and perhaps does not occur 

 at all. The milk gland is not an excretory organ designed 

 for the purpose of getting rid of waste products, and there is 

 no reason for believing that bacteria circulating in the blood 

 will be secreted through the milk gland, provided the milk 

 gland is itself in a normal, healthy condition. Bacteria pass 

 through the gland only when it is itself the seat of inflam- 

 matory trouble. It is probable that in all cases .where the 



